Q: I am hoping you would have a recommendation on how I should deal with the accumulation of moisture on my anodized aluminum patio doors. The back of the house where the patio doors are faces east. The patio doors lead to a wooden deck on the second floor. The window coverings are drapes with sheers.
During winter or after cold nights, I find a lot of moisture and water around the aluminum frames and windows of the patio doors, especially at the sill. Although I wipe it up every day, this water has caused discoloration in the carpeting and some mildew or mold in the walls adjacent to the door frames.
How would you solve this problem? I noticed that the downstairs patio door directly under the upstairs doors does not accumulate any water, and the rest of the windows in the house do not accumulate as much.
Should I replace those doors with ones of a different material, such as vinyl or wood? The furnace is normally turned down or off at nights. I thought the problem might be caused in part by the difference between the outside and inside temperatures. This problem does not occur when the nights are warm and the outside and inside temperatures are fairly even.
A: You’re on the right track. The cause of the wet aluminum and soggy carpet is condensation. Condensation occurs when the temperature difference between cold outside air and warm inside air causes moisture to be wrung out of the humid winter air. Water condenses on the warmer interior glass and frame and puddles at the bottom of the door.
It’s good you’re religious about wiping up each morning. You’re also wise to seek a solution to the problem. Discolored carpet is bad enough. But the wet rug could damage the floor beneath. Given enough time, it could result in the plywood subfloor delaminating, or yet more mold or dry rot.
It’s interesting you note that only the second-floor bedroom has the problem while the door on the first floor does not. Two things cause this phenomenon. Since the opening faces east and the winter sun is low in the sky, our bet is that that doorway gets very little sunshine and is always cold. Secondly, heat rises, so the bedroom will remain warmer longer. And if the drapes are closed, this exacerbates the problem.
There are a couple of things you can do to alleviate the problem. The simple fix that we’d try first is to open a window and open the drapes. The goal is to increase the ventilation enough to eliminate the condensation. If the drapes are closed, warm air can be trapped between the drape and the window.
If you’re uncomfortable with the drapes open or if you’re too cold, the next alternative is to replace the door. The double-paned, high-energy efficiency glass you replace the 1960s aluminum single model with will eliminate the condensation problem. It will be expensive, but you won’t be mopping the floor anymore.
We’d shy away from solid wood, as there are other attractive water-resistant alternatives, including vinyl and aluminum-clad models that should withstand the test of time. To find out which one might best suit your needs, look up "sliding patio doors" on the Internet and you’ll find links to all the major manufacturers.
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